Srimad-Bhagavatam: Canto 11 - Chapter 1 - Verse 3
Sanskrit:
सङ्गं न कुर्यादसतां शिश्नोदरतृपां क्वचित् ।तस्यानुगस्तमस्यन्धे पतत्यन्धानुगान्धवत् ॥ ३ ॥
ITRANS:
saṅgaṁ na kuryād asatāṁśiśnodara-tṛpāṁ kvacittasyānugas tamasy andhepataty andhānugāndha-vat
Translation:
One should never associate with materialists, those dedicated to gratifying their genitals and bellies. By following them one falls into the deepest pit of darkness, just like a blind man who follows another blind man.